Solve Plant Problems Without Pesticides

Choose plants that are hardy to your zone. The map shows USDA Hardiness Zones in Oregon. Hardiness zones range from 1 to 11. Lower numbers in the scale relate to colder environments. Higher numbers relate to warmer environments. Choose plants hardy to your zone or a lower number.

Expect aberrant weather patterns. The photo shows snow on an apple tree that has already blossomed. With climate change, we can expect aberrant weather patterns that will affect plants.

Install plants in spots that have the right amount of sun. The photo shows a rhododendron plant grown in full shade. Its stems are flopping and leaves are sparse.

In comparison, the rhododendron in this photo is healthy. It has strong branches supporting dense, compact foliage. The plant is growing in an inland area with partial shade, ideal for rhododendrons.

The leaves of this rhododendron are burned from too much sunlight. The plant is suffering from drought stress. Rhododendrons planted in full sun away from coastal areas are often damaged by these conditions.

The photo shows an area with exposed soil, ready for landscaping. Large soil clods and standing water indicate slow soil drainage. Choose plants that tolerate wet soil for this area. Or fix the drainage by grading it to sheet water and/or importing soil to build raised planting areas.

If you have an area with slow or poor drainage, choose plants that tolerate seasonally wet or saturated (throughout the year) soil conditions. The red osier dogwood (Cornus sericea) shown in the photo tolerates wet soil conditions.

The photo shows a constructed rain garden, including a swale that captures and absorbs runoff from the roof of the house. Wetland plants such as slough sedge are planted in the swale bottom where the soil is saturated for weeks or months. Plants that require faster soil drainage are planted on the swale berm.

The photo shows a planted area that includes mounds that provide fast soil drainage. The plants chosen for the site don’t tolerate saturated soils at any time in the year. They require moist, well-drained soil to thrive.

Plants adapted to dry environments (little available soil water conditions) often require excellent soil drainage to thrive. Improve soil drainage when the seasonal rain and native soil conditions of your site don’t match the dry environments of plants from dry areas.

The photo shows a blueberry plant suffering from iron deficiency. This condition is often a result of a soil pH higher than blueberries’ preferred pH range. Blueberries need soil with a pH of 4.0–5.5 to thrive. Test your soil pH before planting blueberries. Add sulfur to the soil surface based on soil test recommendations. Adding sulfur lowers the soil pH.

The photo shows tomatoes with blossom end rot. Blossom end rot is caused by a calcium deficiency or other calcium uptake problems in the soil. In the acidic soils of the Pacific Northwest west of the Cascade Mountains, blossom end rot is commonly associated with soil pH below the optimal range for vegetables. Irregular watering causes soil moisture levels to fluctuate. Dry soil prevents roots from taking up calcium. Water regularly and apply mulch to prevent blossom end rot.

Linden trees (Tilia spp.) are prone to damage from aphids. Aphids feed on the leaves and create a sticky residue. The residue encourages the growth of black sooty mold. Linden trees that are attacked by aphids will make a mess if the tree is growing over patios and parking areas. Don’t plant linden trees in areas where the sticky residue and sooty mold are intolerable.

The rose in the photo has black spot (a fungal disease). Leaves and stems develop black spots during wet, warm weather. Severely infected leaves turn yellow and fall off the plant. This disease is common west of the Cascade Mountains in the Pacific Northwest.

The leaves of the roses at a public rose garden don’t show blackspot symptoms. Roses that are resistant to blackspot are less likely to be impacted by the disease. Choose resistant varieties in areas where blackspot is a known issue. See Rose Cultivar Resistance  (PNW Plant Disease Management Handbook).

Some rhododendron varieties are damaged by root weevils, a pest insect for landscape shrubs. The photo shows rhododendron leaves with notches along the leaf edges. This damage is caused by root weevils.

Rhododendron varieties that aren’t damaged by root weevils are available. For example, the variety ‘P.J.M.’ is resistant to root weevils. Choose root weevil-resistant varieties of rhododendron to minimize damage from these pests.

Many popular apple varieties are impacted by apple scab disease. For example, ‘Red Delicious,’ ‘Golden  Delicious,’ ‘Fuji,’ and ‘Braeburn’ varieties are susceptible to apple scab.

Apple varieties such as ‘Liberty,’ ‘Enterprise,’ ‘Easy-Gro,’ and others resist apple scab effectively. Other varieties resist it to varying degrees. Choose resistant varieties in areas where apple scab is an issue.

Inspect plants to ensure they don’t show signs of damage. The photo shows a hydrangea plant in a 1-gallon container. The branches and leaves are full and compact. Check new plants for insects, diseases, and weeds and reject problem plants.

Check the roots of container-grown plants. The photo shows the roots of two plants grown in 1-gallon containers. The plant on the left has roots that just fill the container. The plant on the right is root-bound. The roots are thicker and wrap around the edge of the pot.

The broccoli plants on the left are green, showing new growth. The broccoli plants on the right show signs of stress. The leaves are pale green, yellow, and red. Avoid planting stressed annual vegetables and flowers. They won’t perform well. And they are more likely to be damaged by insect pests and diseases.

Spread compost over the area where you want to install new plants. Mix the compost in as deeply as possible. Add soil amendments such as lime and N-P-K fertilizer as needed. Then dig holes in the amended soil. Install the new plants. Use bagged compost for smaller jobs. A single 1-cubic-foot bag of compost will cover an area 2.5 feet long x 2.5 feet wide (5 square feet) with 2.4 inches of compost.

For large areas or compacted soil, consider using heavy equipment. The backhoe shown in the photo effectively mixes compost into a minimum soil depth of 1.5-2 feet. Get bulk compost delivered for bigger jobs. Before digging with a tractor, locate utilities in the area. Request a utility locate before you dig.

Root-bound trees and shrubs fail to grow vigorous roots and stems. The photo shows a bare root tree with tangled roots wrapping around the root crown. Inspect trees and shrub roots before you purchase them. Avoid root-bound plants. If root-bound plants are your only option, prune the roots and separate them apart before planting.

The photo shows newly installed landscape plants experiencing drought stress. Plants need consistent water after planting to establish and grow.

The photo shows a watering bag. Watering bags release water slowly, which helps newly installed plants to establish.

Drip irrigation provides an effective and convenient way to provide water to plants.

The photo shows example soil test results, including soil pH, percent organic matter, and nutrient analysis.

Provide lawns with water and nutrition. Apply seed over the top of your lawn (overseed) at least every other year. Following product instructions, apply slow release fertilizer, if needed, in spring or fall or both.  Avoid summer fertilizing as it can lead to harmful algal blooms.

Mulch conserves water and suppresses weed seeds from germination. It improves soil structure over time. Carbon-rich mulches like wood chips, bark dust, and straw are less likely to support weed seedlings.

When compost is used as a mulch, weeds sprout and grow as shown in the photo. Compost is an amendment that is mixed into the soil before planting.

Clean up fallen fruits to help disrupt pest and disease cycles. The photo shows apples on the ground with insect damage (signs of codling moth and apple maggot infestation). Raking up and removing fallen apples helps to break the pest life cycle. Fewer pests will emerge next spring.

Rake up and dispose of diseased leaves. The photo shows leaves infested with rose black spot being raked into a bag.

Don’t compost diseased or pest-infested plants on your site. Put them in your green waste recycling bin as shown in the photo. Or take pest- and disease-damaged plant material to your local composting facility.

The photo shows kale plants growing with many weeds. Weeds growing close to desired plants compete for light, water, and nutrients. Stressed plants are prone to pest and disease damage.

The photo shows a landscape area with many spring-flowering weeds. This site will look better and desirable plants will thrive if weeds are removed. Adding mulch to the soil surface after weeding would help to suppress weed growth.

Some plant diseases can transfer from one plant to another on pruning tools. Prune healthy plants before diseased ones. Disinfect pruner blades after pruning infected plants. Keep pruner blades sharp for clean pruning cuts that heal quickly.

Clean your tools when you move from one site to another. Brush off dirt to keep from spreading weed seeds between sites. Maintain your tools over time. Apply oil to the metal and wood handles.

An example crop rotation is to grow peas followed by tomatoes and then cabbage as shown in the photo.

Plant collars protect young plants from pests such as cutworms. Make collars from toilet-paper tubes, paper cups, or cans. Place the tubes over the seedlings and press the end 1 inch into the soil.

Wire fencing is another way to protect plants from pests such as rabbits, birds, and deer.

Fabric plant cages keep flying pest insects from laying eggs on plants. The frame can be wood, wire, PVC pipe, or a tomato cage. Cover it with row cover fabric, cheesecloth, or organza fabric. Pull the fabric tight around the frame and staple or clip it in place.

Slugs and snails are repelled by a copper barrier. The wider the barrier, the better. The copper surface works best if it is kept clean.

Sticky barriers can prevent insect pests from climbing up or down a tree trunk. This stops adults from climbing up to feed, and larvae from crawling down to pupate.

Row cover fabric can protect rows of crops from pests. Support row cover with wire, metal, or plastic hoops. It can also be draped over plants without a supporting structure.

Weigh down the edges of the row cover fabric with boards, bricks, or soil. The goal is to prevent pests from crawling under the row cover. The weight helps to secure the fabric from blowing away.

Use bird netting to protect crops from birds. Use metal or plastic hoops to support bird netting.

Gophers feed on the roots of many types of plants, including fruit trees. If gophers are a known problem in your area, use wire baskets to exclude them from the roots of new trees as shown in the photo.

The photo shows a sturdy netting with pipe frames to protect garden beds. The device excludes squirrels and birds from the desired plants.

Voles (meadow mice) damage fruit tree plants by gnawing on the bark at the base of trees. Protect young fruit trees and grape vines from vole-girdling damage. Use cylinders made from hardware cloth, sheet metal, or heavy plastic (shown in photo) that surround the trunk.

Install sturdy fencing to exclude deer and elk from your garden, orchard, and landscape as needed. Fences exclude domestic animals such as chickens and dogs.

Pick off larger pests, such as slugs, tomato hornworms, and cabbage moth larva (shown in photo). Drop them into soapy water.

Squashing aphids by hand is a quick and easy way to deal with them. When squashed, aphids release chemicals that attract beneficial insect predators.

For scale insects, scrape off insects with your fingertip or plastic edge. Scrape scale insects into soapy water.

Use trapping methods for slugs, snails, and other soil-dwelling pests. The photo shows a beer trap for slugs.

The spotted wing drosophila (SWD) fruit fly poses a challenge for strawberries, blueberries, and raspberries and other thin-skinned fruit. Use easy-to-make traps with vinegar to monitor for SWD. Placing numerous traps in and around your berry crop areas captures many SWD fruit flies.

Use a high-pressure water spray on infested leaves. A strong stream will remove and injure aphids, lace bugs, and other soft-bodied insects. Spray the undersides of the leaves. Repeat as needed.

Prune out tent caterpillar colonies (shown in photo).

Prune out diseased, dead, and dying branches on trees and shrubs.

Small tillers such as the one shown in the photo are useful for controlling soil-borne slugs, symphylans, and insects such as armyworms and cutworms.

Symphylans are soil-borne, insect-like organisms that feed on the roots of vegetable crops. They become a problem when a lot of organic matter (compost) has been added to the soil.

Cutworms and armyworms are both larva of moth species. They lay their eggs in groups. When the eggs hatch, the larvae move across the landscape en masse.

If you have many boxelder bugs or BMSBs on or in your structure, clean them up.

Use a vacuum cleaner to remove boxelder bugs from your structures. Alternatively, hand-pick or sweep them up. Put the debris in a sturdy plastic bag and dispose of it in the trash.